It is proposed to study the effect of antiserum (in the presence or absence of complement) and of lymphocytes, leukocytes and monocytes (from normal and infected rats) on the release of Cr51 from Nippostrongylus brasiliensis worms or larvae in vitro. The purpose of the study is to determine whether antiserum, or the various cell types, are involved in mediating damage sustained by worms or larvae in vivo. We are especially interested in the possibility that IgE anti-worm antibodies may mediate tissue injury in conjunction with either macrophages or eosinophil. Preliminary experiments indicate that it is possible to maintain larvae and worms in tissue culture for several days, thus allowing the above experiments to be carried out with the same batch of parasites. A second phase of this work concerns the evaluation of the influence of immunization on the intestinal uptake of macromolecules. We have previously shown that oral and parenteral immunization with protein antigen leads to a consistent and specific decrease in antigen uptake by everted gut sacs prepared from the jenunum and ileum of rats. We now plan to test whether the uptake of worm antigens is involved in triggering the self-cure reaction observed in rats during infection with N. brasiliensis. In addition, we plan to study whether the persistence of a small chronic infection is associated with the inhibition of uptake of worm antigen from the gastrointestinal tract into the systemic circulation. BIBLIOGRAPHIC REFERENCES: Carson, D., Metzger, H. and Bloch, K.J. Serum IgE levels during the potentiated reagin response to egg albumin in rats infected with Nippostronglylus brasiliensis. J. Immunol. 114: 521-523, 1975. Walker, A.W., Wu, M., Isselbacher, K.J. and Bloch, K.J. Intestinal uptake of macromolecules: III Studies on the mechanism by which immunization interferes with antigen uptake. J. Immunol 115: 884-891, 1975.